ABSTRACT
Osteoporosis is a skeletal disease defined by low bone mass, reduced bone mineral density, and altered bone geometry, whose prevalence is attaining epidemic dimensions in developed countries. Between the age of 20 and 30 years, a peak in bone mass and density is attained, after both mass and density decline with age. This process is accelerated after the menopause, leading in many cases to osteoporosis. The rate and magnitude of bone loss may differ markedly from one skeletal site to another, depending, among other factors, on local mechanical stress. Several investigations have shown that sports eliciting high impact forces, at elevated strain rates, in varied directions, are the most osteogenic (Burr et al., 2002). However, the benefit from a mechanically appropriate sport, depends also on the duration of sport participation, as we have recently observed (Dorado et al., 2003). Adherence to physical activity in aged people declines when the exercise requires the development of high strength levels which have proved to be the most effective in increasing bone mineral density, (Suominen, 1993; Humphries et al., 2000). Moderate or low intensity activities have positive effects in muscular strength, but variable effect in bone (Kerr et al., 1996); and unfortunately, daily activities such as walking, are the less effective (Suominen, 1993; Humphries et al., 2000).
